This invention relates in general to pivot door-type aircraft turbine engines and, more particularly, to such a pivoting thrust reverser door arrangement which includes mechanisms to prevent accidental deployment in flight.
Modern aircraft fan jet engines have a nacelle or shroud surrounding the engine, spaced outwardly from the core engine cowl to define an annular passage or duct for flow of air rearwardly from the fan portion of an enlarged axial flow compressor. In this type of engine, a large proportion of the total thrust is developed by the reaction to the air driven rearward by the fan and the balance results from ejection of the exhaust gas stream from the engine.
Aircraft using engines of this type tend to have high landing speeds, placing great stress on wheel braking systems and requiring very long runways. To reduce this braking requirement and permit use of shorter runways, means are now provided in such engines for reversing at least a major portion of engine thrust during the landing roll. Many different types of thrust reversers have been designed, of varying effectiveness.
One type, primarily used with non-fan type turbine engines, uses large, sturdy clam shell-like blocker doors which swing directly behind the jet exit nozzle and diverge forwardly to reverse thrust. This system must be very heavy and strong and is not easily applied to fan jet engines.
Another type of thrust reverser uses cascade sets in the sidewalls of the shroud or deflector housing with devices for uncovering the cascades and blocking airflow through the annulus aft of the cascades to direct airflow through the cascades, which turn the airflow in a reverse direction. Typical cascade-type thrust reversers include those disclosed by Montgomery in U.S. Pat. No. 4,145,877 and Hom et al in U.S. Pat. No. 3,500,646. While often effective, these systems are mechanically complex, requiring a great many cooperating components. Failure of these components could in some cases cause actuation in flight.
Still another design uses pivotable doors lying in openings in the sidewall of the shroud or nacelle which pivot outwardly while a second set of doors pivot inwardly to block flow of air through the duct and direct it to the outwardly extending door which direct airflow rearwardly. Typical of these is the system disclosed by Ellis in U.S. Pat. No. 3,612,401. This system, while useful, tends to be heavy and mechanically complex, so that the possibility exists of system failure and at least partial thrust reversal occurring in flight.
Yet another design uses a plurality of pivotable doors located in openings arranged radially around the shroud. Each door pivots so that one end contacts the engine cowl blocking airflow through the annular duct while the other end extends outside the nacelle in a direction directing airflow rearwardly. Typical of these is the system disclosed by Maison et al in U.S. Pat. No. 3,605,411. While having greater mechanical simplicity than other systems, it is difficult with this arrangement to provide optimum duct airflow blocking and optimum flow re-direction in the reverse direction. Accidental release of stowage latches or failure of other components could cause inadvertent actuation.
Thus, there is a continuing need for improved thrust reversing systems for use in ducted fan jet engines which combine highly effective flow reversal with low cost, light-weight, mechanical simplicity, ease of maintenance and prevention of accidental deployment due to system failures.